First off, your wife is a keeper!!
Secondly, your situation is giving me a headache!
I would consider going with the mts 5.0 and 1 pb13+ for now, putting the money towards a better receiver and add the 2nd pb13+ later. Or possibly substituting 2 Rythmik 15's for the 2 pb13's.
The onkyo 606 and ext. amp would work, but I am not certain the 606 dac's, ps, etc. are at the same performance level of the mts. The external amp complicates the setup. Unless you are planning going with a real pre/pro setup later, I personally would keep it simple and just get another receiver.
Of course, there are other factors at play here, such as svs package discounts, etc., and that's why I have a headache.
Excuse me, I need to go take a couple of aspirins.